Washington
— Two fundamental questions arise in the wake of the collapse of the Iceland meeting between President Ronald Reagan and Soviet leader Mikhail Gorbachev: Can the President persuade the American people, the United States Congress, and the European allies that his technological dream of an antimissile defense system, so-called ``star wars,'' better serves US national security than deep reductions in strategic offensive weapons, which the Soviets are prepared to make?

Will the President come up with a counterproposal to Mr. Gorbachev's take-it-or-leave-it offer, which will give higher priority to offensive weapons and make it possible to keep the US-Soviet arms dialogue going?

There is a general gloom in Washington that the two leaders failed to reach an arms understanding in Reykjavik, thereby shattering prospects for an early full-scale summit meeting in the US. Diplomatic experts fault both sides for trying to do too much in a two-day meeting and letting it become a showdown.

Gorbachev is criticized for resorting to a squeeze play on the President's Strategic Defense Initiative (SDI), as star wars is formally known. Even though substantial progress was made toward agreements on reductions in strategic weapons, cuts in medium-range missiles, and nuclear testing -- and although the President committed himself to a 10-year moratorium on deployment of SDI -- the Soviet leader opted to play an all-or-nothing game. He refused to agree on nuclear arms cuts unless the US limits SDI to laboratory research.

``That's a dangerous approach for a superpower,'' says William Hyland, once a high aide to former Secretary of State Henry Kissinger. ``If that's his style, perhaps we can't do business with him.'' On the other hand, say Mr. Hyland and other Soviet experts, the President should not have made a quick decision on the far-reaching proposals offered at Reykjavik, but brought them back for study and debate. Then matters would not have ended in frustration and disappointment.

But impatience seems to have governed both men. Gorbachev was determined to make clear what price the US will pay if it proceeds with the testing and development of SDI, a nationwide system designed to protect against incoming missiles and that many scientists say is not feasible. That price is failure to achieve substantial cuts in nuclear arsenals.

``He's laid all those cards on the table, and we know now what we can get if we accept limits on SDI,'' says Mark Garrison, a former US diplomat in Moscow.

Progress was made in several nuclear areas:

On strategic offensive weapons, the two agreed tentatively to a 50-percent reduction in bombers, warheads, and missile launchers.

On medium-range forces, Gorbachev agreed to a global limit of 100 warheads on each side, with the USSR deploying its 100 in Asia and the US its 100 on its own soil. This would result in the zero deployments in Europe that the US initially sought and would require the Soviets to scrap more than 1,000 warheads atop their massive SS-20s. The Soviets also offered to reduce the number of shorter-range missiles in Europe, which the US also wanted. And they agreed the interim accord would stay in effect until replaced by a new one.

On nuclear testing, the Soviets accepted the US proposal to seek a step-by-step accord, starting with verification of existing limited test-ban treaties and working toward a reduction in the number of tests.

The two sides also agreed not to withdraw from the Anti-Ballistic Missile (ABM) treaty for a period of 10 years, a compromise between the 7 years the US sought and the 15 years the Soviets wanted.

These impressive gains generated an initial feeling of optimism. But all these proposals were linked to SDI, and it was this issue that blocked agreement.

The President said he would be willing to reduce his SDI program if the two sides agreed to eliminate all ballistic missiles over the next 10 years. But he also insisted that research, testing, and development continue on SDI, which he said were permitted under the ABM treaty. Gorbachev sought to rule out all testing and development and to limit research to the laboratory. Further disagreement arose over what defensive systems would be permitted at the end of 10 years, with the US insisting some defense would be needed in case of cheating or attacks by third countries.

Now that he has forcefully played his cards, Gorbachev doubtless hopes Congress, the American public, and the European allies will put pressure on the Reagan administration to back down from its present stance. One source of likely pressure will be knowledgeable lawmakers in the Senate, including Sen. Sam Nunn (D) of Georgia, who are looking into the historical record of the ABM treaty negotiations.

At issue in the whole debate over SDI is interpretation of the treaty, which prohibits the testing, development, and deployment of exotic weapons based in space. Reagan so far has adhered to the strict interpretation of the pact followed by administrations since 1972. But he has given himself legal latitude for testing and developing SDI by claiming a looser interpretation. Hence the desire of the Soviets to strengthen the treaty.

Arms control experts criticize the President for trying to reinterpret the ABM pact to permit the star wars program, although they acknowledge that some language in the pact is vague and should be reworked. They also assail Reagan's proposal in Reykjavik to eliminate all nuclear weapons in 10 years, deeming this an unrealistic and even dangerous proposal, for it would leave the Soviet Union with superior conventional forces.

``The proposal is a sad note of political posturing or naive faith and that's disturbing . . .,'' says Alton Frye of the Council on Foreign Relations. ``The notion of zero ballistic missiles strikes me as a totally unfounded and misleading expectation for people to pursue.''